package hrc.heart_rate_monitor;


public abstract class ImageProcessing {

	private static int decodeYUV420SPtoRedSum(byte[] yuv420sp, int width, int height) {
		if (yuv420sp==null) return 0;
		
		final int frameSize = width * height;

		int sum = 0;
	    for (int j = 0, yp = 0; j < height; j++) {
	        int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
	        for (int i = 0; i < width; i++, yp++) {
	            int y = (0xff & ((int) yuv420sp[yp])) - 16;
	            if (y < 0) y = 0;
	            if ((i & 1) == 0) {
	                v = (0xff & yuv420sp[uvp++]) - 128;
	                u = (0xff & yuv420sp[uvp++]) - 128;
	            }
	            int y1192 = 1192 * y;
	            int r = (y1192 + 1634 * v);
	            int g = (y1192 - 833 * v - 400 * u);
	            int b = (y1192 + 2066 * u);

	            if (r < 0) r = 0; else if (r > 262143) r = 262143;
	            if (g < 0) g = 0; else if (g > 262143) g = 262143;
	            if (b < 0) b = 0; else if (b > 262143) b = 262143;

	            int pixel = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) & 0xff00) | ((b >> 10) & 0xff);
	            int red = (pixel >> 16) & 0xff;
	            sum+=red;
	        }
	    }
	    return sum;
	}
	
	public static int decodeYUV420SPtoRedAvg(byte[] yuv420sp, int width, int height) {
		if (yuv420sp==null) return 0;
		
		final int frameSize = width * height;

		int sum = decodeYUV420SPtoRedSum(yuv420sp,width,height);
		return (sum/frameSize);
	}
}
